Links in a telephone networking system, such as an SS7 network, work by load sharing, i.e. each link takes up a known percentage of the total load. Within each link, there are generally five sequences that provide identification/routing information about a signaling message being transmitted over the network. In other words, five messages are used to set-up and release trunk circuits in a service switching point (SSP), namely: Initial address message (IAM), address complete message (ACM), answer message (ANM), release message (REL), and release complete message (RLC). These five sequences or messages make up phone call recognition, as generally known in the area of SS7 networks and the like.
An SS7 network is more formally referred to as a Common
Channel Signaling System No. 7 (i.e., SS7 or C7), which is a global standard for telecommunications defined by the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T). The standard defines the procedures and protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup, routing and control. The ITU definition of SS7 allows for national variants such as the American National Standards Institute (ANSI) and Bell Communications Research (Telcordia Technologies) standards used in North America and the European Telecommunications Standards Institute (ETSI) standard used in Europe. The SS7 and C7 standards listed above are incorporated herein by reference in their entirety.
The SS7 network and protocol are used for: basic call setup, management, and tear down; wireless services such as personal communications services (PCS), wireless roaming, and mobile subscriber authentication; local number portability (LNP); toll-free (800/888) and toll (900) wireline services; enhanced call features such as call forwarding, calling party name/number display, and three-way calling; and efficient and secure worldwide telecommunications.
When a network supervisor wishes to investigate a telephony network interruption or delay, he or she will generally resort to an element manager to perform a “call trace.” The element manager or managers may be employed as watchdogs in a telephony system, and the term “call trace” refers to the task of understanding how one connection is made to another within the network channels.
When an IAM message is detected on one link, the processor, sometimes referred to as a probe, detecting the IAM message must send a trigger message to other probes monitoring other links because other signaling messages, ACM, ANM, REL, and RLC messages, may take other link paths due to the load sharing on the SS7 network. After the IAM message containing one of the code—sorigination point code (OPC), destination point code (DPC), or circuit identification code (CIC))—has been identified in a given link set (i.e., all links between, for example, a given SSP and a given STP, see FIG. 2), there is a fixed amount of time to alert all the probes monitoring the network links that further messages relating to the phone call are likely to be passing imminently. When sending the trigger between monitoring processors via a TCP/IP system, there is a possibility that bottlenecks inherent in the TCP/IP system will cause the trigger to be delayed between the processors. Thus, the ACM message, which follows the JAM message by 100 msec typically, may go undetected by the probes.
Thus, monitoring link sets for messages containing a selected code related to a phone call on a link set can be difficult, if not impossible, particularly when multiple link sets must be monitored and/or viewed by an operator. Furthermore, in present systems, the only way to determine the order of various transmissions is to gather signal information from the signaling messages, store the information in a database, and sort through the stored information for purposes of troubleshooting. This process, of course, does not lend itself to real-time call tracing.
Sophisticated telephone network systems have been disclosed and include various mechanisms for troubleshooting inevitable errors, which occur during operation. For example, U.S. Pat. No. 6,125,177 to Whittaker shows a method and an apparatus for enhancing signaling and call routing between local and remote terminals of a telecommunications network defined by a layered hierarchy of protocols and switching between telephony and Internet services.
U.S. Pat. No. 5,592,530 to Brockman shows a general testing and monitoring system using an SS7 network in the operation of a phone system. This reference deals with problems of having data located at two different nodes and provides a link monitoring system located at STP sites.
U.S. Pat. No. 4,959,849 to Bhusri relates to a method and architecture for surveillance of network systems, which permits quality control for the network system utilizing information within message signal units received by processing elements. U.S. Pat. No. 6,104,801 to Miloslavsky relates to a system for call routing telephony where routing protocols are associated with specific levels of one or more system characteristics. Appropriate routing protocols are selected and executed based upon system condition and performance.